Hydrocarbon conversion process

ABSTRACT

The invention relates to a process for converting hydrocarbons into unsaturated products such as acetylene and/or ethylene. The invention also relates to converting acetylene to olefins such as ethylene and/or propylene, to polymerizing the olefins, and to equipment useful for these processes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No. 13/588,821filed Aug. 17, 2012, now allowed, and claims the benefit of ProvisionalApplication No. 61/538,476 filed on Sep. 23, 2011, and EP ApplicationNo. 11189648.6 filed on Nov. 18, 2011, the disclosures of which areincorporated herein by reference in their entireties.

FIELD

The invention relates to a process for converting hydrocarbons intounsaturated products such as acetylene and/or ethylene. The inventionalso relates to converting acetylene to olefins such as ethylene and/orpropylene, to polymerizing the olefins, and to equipment useful forthese processes.

BACKGROUND

U.S. Pat. No. 2,845,335 discloses a four-step process for converting ahydrocarbon stream to a mixture comprising unsaturated hydrocarbon. Thereactor system comprises four similar regenerative reactors, withreactors one and two comprising a first parallel reactor pair which areseparated from a second parallel reactor pair (reactors three and four)by at least one mixing region. The reactor system is preheated beforethe first step of the process.

In one embodiment, the reference discloses a first step involvingflowing a hydrocarbon through the first reactor pair toward the secondreactor pair, with a first portion of the hydrocarbon flowing throughreactor one and a second portion flowing through reactor two. Pyrolysisproducts flow away from the mixing region, through the second reactorpair, a portion of the pyrolysis products being deposited as coke inreactors one-four. In a second step, fuel and air are conducted towardthe mixing region, the fuel being conducted through reactor three andthe air being conducted through reactor four. The fuel and air combustin the mixing region, with the combustion products flowing away from themixing region through the first reactor pair (a portion of thecombustion products flowing through each of reactors one and two),thereby (i) heating the reactor system for step 3 and (ii) oxidizingcoke deposited in reactors one, two, and four. The third step is similarto the first step, with pyrolysis products flowing away from the mixingregion, through the second reactor pair and again depositing coke inreactors one-four. In a fourth step, fuel and air are again conductedtoward the mixing region, but now the fuel is conducted through reactorfour and the air is conducted through reactor three (the reverse of steptwo). The fuel and air combust in the mixing region, with the combustionproducts flowing away from the mixing region through the first reactorpair, thereby (i) heating the reactor system for step one and (ii)oxidizing coke deposited in reactors one, two, and three.

It is desired to increase the efficiency of the process.

SUMMARY OF THE INVENTION

In an embodiment, the invention relates to a hydrocarbon conversionprocess, comprising:

-   -   (A) heating at least a portion of a reactor to a temperature        ≧800° C., the reactor comprising first and second channels;    -   (B) providing a first mixture to the heated reactor, the first        mixture comprising hydrocarbon, wherein at least a portion of        the hydrocarbon includes alkane;    -   (C) exposing the first mixture to a temperature ≧800° C. in the        heated reactor and abstracting sufficient heat from the reactor        to convert at least a portion of the first mixture's alkane to        combustible non-volatiles and unsaturated hydrocarbon;    -   (D) transferring at least a portion of the unsaturated        hydrocarbon away from the reactor via the first and second        channels, at least a portion of the combustible non-volatiles        being deposited in the first and second channels during the        transfer; and    -   (E) repeating steps (A)-(D); wherein step (A) includes:    -   (i) a first time interval during which fuel and oxidant        exothermically react in the reactor, the fuel being provided via        the first channel and the oxidant being provided via the second        channel, in order to        -   (a) replace at least a portion of the heat abstracted during            step (C) and        -   (b) combust at least a portion of the combustible            non-volatiles in the second channel; and    -   (ii) a second time interval during which additional oxidant is        provided to the reactor via the first channel in order to        combust at least a portion of the combustible non-volatiles in        the first channel.

In another embodiment, the invention relates to a regenerative,reverse-flow pyrolysis reactor comprising,

-   -   (a) first and second reactors, each comprising a unitary reactor        bed;    -   (b) a mixing region located between the first and second        reactors;    -   (c) first and second channels located within the first reactor,        the first and second channels being thermally-connected,        substantially independent flow-paths;    -   (d) a third channel located within the second reactor; and    -   (e) first valve means for directing to the mixing region        -   (i) a first reactant via the first channel during a first            time interval,        -   (ii) a second reactant via a second channel during the first            time interval, and        -   (iii) a first portion of the second reactant via the first            channel and a second portion of the second reactant via the            second channel during a second time interval.

In yet another embodiment, the invention relates to a process forremoving combustible non-volatiles from a reactor system, comprising:

-   -   (A) depositing combustible non-volatiles during a first        conversion step, the combustible non-volatiles being deposited        in first and second conduits of a first reactor, the first        reactor being located within the reactor system;    -   (B) during a first time interval of a second conversion step        -   (a) conducting a first-reactant through the first conduit            and a second-reactant through the second conduit;        -   (b) heating the reactor system by exothermically reacting at            least a portion of the second-reactant with (i) at least a            portion of the combustible non-volatiles located in the            second conduit and (ii) at least a portion of the            first-reactant; and    -   (C) during a second time interval of the second conversion step        -   (a) conducting at least a portion of the second-reactant            through the first conduit; and        -   (b) reacting the second-reactant with at least a portion of            the combustible non-volatiles located in the first conduit.

In yet another embodiment, the invention relates to a hydrocarbonconversion process, comprising:

-   -   (a) providing a first mixture to a reactor, the first mixture        comprising hydrocarbon, wherein (i) the reactor comprises first        and second channels and (ii) at least a portion of the        hydrocarbon includes alkane;    -   (b) exposing the first mixture to a temperature ≧800° C. in the        reactor and abstracting sufficient heat from the reactor to        convert at least a portion of the first mixture's alkane to        combustible non-volatiles and unsaturated hydrocarbon;    -   (c) transferring at least a portion of the unsaturated        hydrocarbon away from the reactor via the first and second        channels, at least a portion of the combustible non-volatiles        being deposited in the first and second channels during the        transfer;    -   (d) exothermically reacting fuel and oxidant in the reactor        during a first time interval, the fuel being provided via the        first channel and the oxidant being provided via the second        channel, in order to        -   (i) replace at least a portion of the heat abstracted from            the reactor during the conversion and        -   (ii) combust at least a portion of the combustible            non-volatiles in the second channel; and    -   (e) providing additional oxidant to the reactor via the first        channel during a second time interval in order to combust at        least a portion of the combustible non-volatiles in the first        channel.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 schematically shows an embodiment of the invention utilizing areverse-flow pyrolysis reactor system.

FIG. 2 schematically shows a reverse-flow pyrolysis reactor useful inthe system of FIG. 1.

FIG. 2A schematically shows a top view of the reverse-flow pyrolysisreactor of FIG. 2.

FIG. 3 schematically shows another reverse-flow pyrolysis reactor usefulin the system of FIG. 1. The reactor includes a plenum that is usefulfor directing the flow of oxidant to the reactor and valve means thatare useful for controlling the flow of gasses to and from the reactor.

FIG. 3A schematically shows a top view of the reactor of FIG. 3.Utilizing a plenum allows a greater separation of Channels 14 and 15compared to the reactor of FIGS. 2 and 2A.

FIG. 4 schematically shows yet another a reverse-flow pyrolysis reactoruseful in the system of FIG. 1.

FIG. 4A schematically shows a top view of the reactor of FIG. 4.

FIG. 5 schematically shows a section view of rectant distributors and areactor bed that can be utilized in the reactor of FIG. 4.

DESCRIPTION

Although U.S. Pat. No. 2,845,335 desirably removes coke from at leastsome of the system's reactors during each of the combustion steps, ithas been found that this benefit is obtained at a considerable loss inprocess efficiency. The Stoichiometry of efficient combustion generallyrequires a combustion mixture comprising significantly more air (highervolumetric flow rate) than fuel. Since reactors three and four of theconventional process are of similar volume, efficient combustion leadsto an air space velocity (GHSV) that is much larger than the fuel GHSVduring the conventional process's second and fourth steps. This leads toa thermal imbalance between reactor's three and four becauseregenerative-bed processes such as heat transfer and heat removal areclosely related to space velocity. Should the second and fourth steps beoperated at substantially equal air-fuel flow rates, to equalize GHSVand reduce the thermal imbalance, the inefficient combustion conditionswould lead to lower temperatures in reactor one and two, which reducesconversion to the desired products.

It has been found that these and other deficiencies in the conventionalprocess can be overcome by utilizing a reactor system comprising firstand second regenerative reactors (each reactor being, e.g., a unitaryreactor bed). The first reactor comprises at least one first conduit andat least one second conduit. During the oxidation step, (i) the firstconduit is a “multi-purpose” conduit, which conveys fuel during a firstinterval of the oxidation step and oxidant during a second interval ofthe oxidation step and (ii) the second conduit is an oxidant conduitwhich conveys oxidant during the oxidation step's first and secondintervals. During the pyrolysis step, the first and second conduitsconvey pyrolysis products in an average flow direction that is thereverse of the average flow of fuel and oxidant. In other words, theprocess comprises two steps (an oxidation step and a pyrolysis step),with the oxidation step comprising at least two substantiallynon-overlapping intervals.

Since the first reactor has a conduit (the second conduit) dedicated tothe flow of oxidant during both intervals of the oxidation step, (i) thecross-sectional area of the multi-purpose conduit can be appropriatelysized for providing the desired oxidant-fuel mixture for combustionduring the first interval and (ii) switching the multi-purpose conduitfrom fuel-flow to oxidant-flow between the first and second intervalscan be accomplished without a significant flow-rate change, therebylessening or even eliminating a thermal imbalance between the conduitsduring the first and second intervals. Besides increased thermalefficiency, decreased thermal imbalance, and increased yield of desiredproducts over the conventional process, the process of the inventionremoves coke deposited in the first and second conduits during theoxidation step, thereby obviating the need for a second oxidation stephaving reversed fuel-air flow, as in the conventional process.

In one embodiment, a first mixture comprising hydrocarbon is provided tothe reactor system during the pyrolysis step. The first mixture ispyrolysed, thereby producing a hydrocarbon-containing pyrolysis product,e.g., second mixture comprising C₂ unsaturates and combustiblenon-volatiles, e.g., coke. A portion of the combustible non-volatilesremain in the first and second conduits, e.g., as a deposit. Optionally,a third mixture is derived from the second mixture, e.g., by separatingfrom the second mixture one or more of molecular hydrogen, saturatedhydrocarbon, etc. The pyrolysis is endothermic, with at least a portionof the heat utilized by the pyrolysis being provided by the reaction ofa fourth mixture in the oxidation step, the fourth mixture comprisingfirst and second reactants. The first reactant comprises fuel, e.g.,molecular hydrogen and/or hydrocarbon. The second reactant comprisesoxidant, e.g., molecular oxygen. A fifth mixture is produced during theoxidation step, the fifth mixture comprising products derived fromoxidation reactions of the fourth mixture, products derived from theoxidation of non-volatiles deposited in the reactor during precedingpyrolysis steps, and any un-reacted fourth mixture. The invention is notlimited to methods for converting hydrocarbon to acetylene and/orethylene. The invention is generally applicable to any process resultingin the conversion of hydrocarbon to coke in a reverse-flow pyrolysisreactor, including those for converting methane under thermal pyrolysisconditions at a temperature ≧1.20×10³° C.

In an embodiment, the first and second conduits each comprise channelswithin a first reactor, e.g., a first reactor bed. While not wishing tobe bound by any theory or model, it is believed that locating themulti-purpose channel and second-reactant channel within a unitaryreactor (the first reactor), as is the case in this embodiment, leads toa considerable improvement in the reactor-system's thermal efficiencyover the conventional reactor, which locates its first and secondconduits in separate reactor beds.

In this embodiment, the oxidation step comprises first and secondintervals. During the first interval of the oxidation step, the firstreactant is conducted through the first reactor via a multi-purposechannel (a first channel) and at least a first portion of the secondreactant is conducted through the first reactor via a second-reactantchannel (a second channel). During the second interval, a first portionof the second reactant is conducted through the multipurpose channel,and a second portion of the second reactant is conducted through thesecond-reactant channel. Optionally, first reactant is conveyed to thereactor system during the oxidation step's second interval, e.g., via(i) a second multi-purpose channel, the second multi-purpose channelbeing utilized to convey second reactant during the first intervaland/or (ii) a first-reactant channel which can be a third channellocated in the first reactor, the first-reactant channel being utilizedsolely for conveying the first reactant during the first and secondintervals. It can be desirable to utilize a first-reactant channel inembodiments where (i) conveying the first reactant does not result inthe accumulation of a significant amount of non-volatiles in thefirst-reactant channel and/or (ii) the second mixture is not conveyedthrough the first-reactant channel during the pyrolysis step.Optionally, the first and second reactants combine downstream of thefirst reactor to produce the fourth mixture during both the first andsecond intervals.

The fuel and oxidant components of the fourth mixture exothermicallyreact to form the fifth mixture, thereby heating (and regenerating) thefirst reactor for the pyrolysis step. The fifth mixture is conductedaway via the channel(s) of the second reactor, which increases thesecond reactor's temperature, thereby regenerating the second reactorfor the endothermic pyrolysis step. Optional flow control means, such asvalve means, sparger means, and/or distributor means, etc., andcombinations thereof can be utilized to direct the first and secondreactants and portions thereof to the designated channels during thefirst and second intervals.

Process objectives will generally dictate the total flow amount (moles,volume, or mass) of first and second reactant passing through thereactor over the course of the oxidation step. This total flow in anoxidation step is carried by the available channels over the availableintervals. When a reactant is conveyed through a plurality of channelsduring an interval, it is understood that each of the channels conveys aportion of the given reactant. Such portions (first, second, etc.) areexpressly identified in certain embodiment for clarity, but it should beunderstood that this description is optional nomenclature.

In another embodiment, the first reactor comprises at least threechannels, one second-reactant channel and two multi-purpose channels.During the first interval of the oxidation step, the first multipurposechannel is utilized for transporting the first reactant. The secondmulti-purpose channel is utilized for conducting a first portion of thesecond reactant and the second-reactant channel is utilized forconducting a second portion of the second reactant. During the oxidationstep's second interval, the second multi-purpose channel is utilized forconducting the first reactant. The second multi-purpose channel isutilized for conducting a first portion of the second reactant and thesecond-reactant channel is utilized for conducting a second portion ofthe second reactant. The first portion:second portion weight ratiodepends, e.g., on the configuration of the reactor system, and canchange from interval-to-interval of the oxidation step. The firstmulti-purpose channel comprises all the passages within the firstreactor that are utilized for transporting the first reactant during thefirst interval and second reactant during the second interval. Thesecond multi-purpose channel comprises all the passages within the firstreactor that are utilized for transporting the second reactant duringthe first interval and the first reactant during the second interval.The second-reactant channel comprises all the passages within the firstreactor that are utilized for transporting second reactant during boththe first and second intervals. After the oxidation step, the fifthmixture is conducted away and the first mixture is conducted to thereactor system for the pyrolysis step.

During the pyrolysis step, the first mixture is conducted to the secondreactor, wherein the first mixture is pyrolysed under thermal pyrolysisconditions to produce the second mixture. A first portion of the secondmixture, e.g., a portion in the vapor phase under the thermal pyrolysisconditions, is conducted away from the reactor system via the channelswithin the first reactor. A second portion of the second mixture, thesecond portion comprising ≧50.0 wt. % of the second mixture'scombustible non-volatiles (e.g., coke), remains in the channels of thefirst reactor, e.g., as a deposit. Deriving the second mixture from thefirst mixture in such a system does not require a catalyst, though onecan be used, e.g., to optionally convert light hydrocarbon (e.g.,propane) in the first mixture to propylene.

In another embodiment, the process comprises an oxidation step, apyrolysis step, and a second oxidation step, with the first oxidationstep operated as in the first interval of the preceding embodiments andthe second oxidation step operated as in the second interval.

Alternating oxidation and pyrolysis steps can be conducted in sequence,e.g., continuously. A feature of the invention is that at least aportion of the combustible non-volatiles deposited in a multi-purposeand second-reactant channels of the first reactor during a pyrolysisstep is removed by oxidation during at least one interval of asubsequent oxidation step.

The pyrolysis and oxidation steps of the preceding embodiments can beoperated in sequence, e.g., periodically or aperiodically. The processcan be operated in batch, semi-continuous, or continuous modes. Theduration of the pyrolysis step is substantially independent of theduration of the oxidation steps. The duration of the first and secondintervals can be substantially the same, but this is not required. In anembodiment, the reactor system operates, e.g., in series, parallel, or acombination thereof, and utilizes accompanying valve means forconducting the first, second, fourth, and fifth mixtures to/from thereactors of the reactor system. For example, in one embodiment reactorsystem includes first and second reactors, oriented in a seriesrelationship with each other with respect to a common flow path,optionally along a common axis. The common axis may be horizontal,vertical, or some other orientation with respect to the surface of theearth.

For the purpose of this description and appended claims, the followingterms are defined. The term “hydrocarbon” means molecules (and mixturesthereof) including both carbon atoms and hydrogen atoms, and optionallyincluding other atoms (heteroatoms) such as oxygen, sulfur, andnitrogen. The term “oxidant” means a composition (e.g., molecularoxygen) that is capable of oxidizing another composition or part thereof(e.g., hydrocarbon or a hydrocarbon mixture). The term “molecularhydrogen” means H₂. The term “molecular oxygen” means O₂.

The term “polymer” means a composition including a plurality ofmacromolecules, the macromolecules containing recurring units derivedfrom one or more monomers. The macromolecules can have different size,molecular architecture, atomic content, etc. The term “polymer” includesmacromolecules such as copolymer, terpolymer, etc. The “Periodic Tableof the Elements” means the Periodic Chart of the Elements as tabulatedon the inside cover of The Merck Index, 12th Edition, Merck & Co., Inc.,1996.

The terms “convert”, “conversion”, “converting”, etc., with respect topyrolysis processes include, e.g., any molecular decomposition,cracking, breaking apart, reformation of molecules, includinghydrocarbon, oxygenate, etc., by at least pyrolysis heat. With respectto non-pyrolysis processes that are at least partly catalytic, the termconversion includes, e.g., hydroprocessing (such as hydrogenation,hydrotreating, etc.), hydroformylation, catalytic separation, etc.

The term “pyrolysis” means an endothermic reaction for convertingmolecules into (i) atoms and/or (ii) molecules of lesser molecularweight, and optionally (iii) molecules of greater molecular weight,e.g., processes for converting hydrocarbons such as methane, ethaneand/or propane to molecular hydrogen and unsaturates such as ethylene,propylene and acetylene.

The terms “reactor”, “reactor system”, “regenerator”, “recuperator”,“regenerative bed”, “monolith”, “honeycomb”, “reactant”, “fuel”, and“oxidant” have the meanings disclosed in U.S. Pat. No. 7,943,808, whichis incorporated by reference herein in its entirety. The term “pyrolysisreactor”, as used herein, refers to a reactor, or combination or systemthereof for converting hydrocarbons by at least pyrolysis. With respectto pyrolysis reactors, the term “residence time” means the average timeduration for non-reacting (non-converting by pyrolysis) molecules (suchas He, N₂, Ar) having a molecular weight in the range of 4 to 40 totraverse a pyrolysis region of a pyrolysis reactor. The term “pyrolysisstage” means at least one pyrolysis reactor, and optionally includingmeans for conducting one or more feeds thereto and/or one or moreproducts away therefrom. With respect to reactors, the term “region”means a location within a reactor, e.g., a specific volume within areactor, a specific volume between two reactors and/or the combinationof different disjointed volumes in one or more reactors. A “pyrolysisregion” is a region for conducting pyrolysis. The pyrolysis region caninclude, e.g., one or more conduits, channels, or passages. The term“conduit” refers to means for conducting a composition from one locationto another. The term encompasses (i) elementary conducting means, suchas a pipe or tube, and (ii) complex means such as tortuous pathwaysthrough conducting means, e.g., pipes, tubes, valves, and reactors, thatare filled with random packing. The term “passage” means a geometricallycontiguous volume element that can be utilized for conveying a fluidwithin a reactor, regenerator, recuperator, regenerative bed, monolith,honeycomb, etc. The term “channel” means a plurality of passages thatcan be utilized together for conveying a fluid within the reactor,regenerator, recuperator, regenerative bed, monolith, honeycomb, etc.For example, a honeycomb monolith can comprise a single channel, thechannel having a plurality of passages or sets of passages, e.g.,hundreds of thousands of passages per square meter of the honeycomb'scross-section.

The term “thermal pyrolysis” means <50.0% of the heat utilized by thepyrolysis is provided by exothermically reacting the pyrolysis feed,e.g., by exothermically reacting an oxidant with hydrocarbon and/orhydrogen of the first mixture. The term “thermal pyrolysis reactor”means a pyrolysis reactor wherein ≧50.0% of the heat utilized by thepyrolysis is provided by heat transfer from reactor components, e.g.,solid surfaces associated with the reactor such as tubulars or bedmaterials; optionally ≧80.0% or ≧90.0% of the heat utilized by thepyrolysis is provided by such heat transfer. Optionally, an exothermicreaction (e.g., combustion) occurs within the thermal pyrolysis reactor.

The term “high-severity” with respect to the pyrolysis of a feedcomprising hydrocarbon, e.g., the first mixture, means pyrolysisoperating conditions resulting in the conversion to acetylene of ≧10.0wt. % of the feed's hydrocarbon based on the total weight of hydrocarbonin the feed. The operating conditions for a thermal pyrolysis reactormay be characterized by a severity threshold temperature that divideslow-severity operating conditions in thermal pyrolysis reactors fromhigh-severity operating conditions in thermal pyrolysis reactors. Theseverity threshold temperature is defined as the lowest temperature atwhich the feed to the reactor may react at a residence time ≦0.1 secondto make at least 10.0 wt. % acetylene as a percent of the hydrocarbonsin the mixture evaluated at the given operating conditions of theprocess. The high-severity operating conditions for a thermal pyrolysisreactor may be characterized as peak pyrolysis gas temperatures that aregreater than the severity threshold temperature. The low-severitythermal pyrolysis reactor may be characterized as pyrolysis gastemperatures that are less than the severity threshold temperature andno pyrolysis gas temperatures that exceed the severity thresholdtemperature. For example, for the thermal conversion of a methane feedat a pressure of 14.7 psig (101 kPa) and with 2:1 molar ratio ofmolecular hydrogen to methane, the threshold temperature is about 1274°C. for this process. At temperatures at or above 1274° C., yields ofacetylene can exceed 10.0 wt. % of feed hydrocarbon, at some time ≦0.1seconds. Conversely, at temperatures below 1274° C., there are no times≦0.1 seconds for which yields of acetylene reach 10.0 wt. % of themethane.

The term “peak pyrolysis gas temperature” means the maximum temperatureachieved by the bulk pyrolysis stream gases as they travel through thepyrolysis reactor (e.g., cracking region or radiant region). One skilledin the art will appreciate that temperatures immediately proximate to apartition may be higher, and may, in some infinitesimal boundary layer,actually approach the solid temperature. However, the pyrolysistemperature referred to herein should be considered a bulk gastemperature, which is a temperature that could be measured by a device(such as a thermocouple) that is not in contact with the solid material.For example, if the gas is traveling through tubulars in a thermalpyrolysis reactor, the bulk gas temperature may be taken as the averagetemperature over any tubular cross-section, and the peak pyrolysis gastemperature as the highest cross-sectional-average temperature of thepyrolysis stream.

In an embodiment, a second mixture is derived by pyrolysis of a firstmixture, the first mixture being derived from one or more sourcematerials. The term “source materials” means sources comprisinghydrocarbon. Examples of source materials comprising hydrocarbon includeone or more of hydrocarbon derived from petroleum; syngas (a mixturecomprising carbon monoxide and hydrogen); methane; methane-containingstreams, such as coal bed methane, biogas, associated gas, natural gas,and mixtures or components thereof; synthetic crudes; shale oils; orhydrocarbon streams derived from plant or animal matter. Suitablehydrocarbon source materials include those described in U.S. Pat. Nos.7,943,808 and 7,544,852, which are incorporated by reference herein intheir entirety.

The term “hydrogen content” of a mixture or source material means atomichydrogen bound to carbon and/or heteroatoms covalently bound thereto andwhich excludes molecular hydrogen (H₂) in the mixture (or sourcematerial) expressed as a weight percent based on the weight of thehydrocarbons in the mixture (or source material). Optionally, one ormore mixtures and/or source materials comprises non-volatiles. The term“non-volatiles” means molecules and mixtures thereof having a nominalatmospheric boiling point ≧570.0° C., e.g., refractory oxygenates,refractory hydrocarbon, metals, minerals, etc. American Society ofTesting and Materials (“ASTM”) methods can be used to determine thenominal atmospheric boiling point (ASTM method 1078) and the amount andproperties of such non-volatiles, such as ASTM methods D-6560, D-7061,D-189, D-482, D-524, and D-2415. Non-volatiles that are capable of beingcombusted are called “combustible non-volatiles”. The term non-volatilesencompasses, e.g., coke, ash, soot, resid, metal, mineral, ash,ash-forming asphaltenic, tar, etc., including those formed, e.g., duringor after oxidation (e.g., combustion or partial oxidation) and/orpyrolysis, including those which may remain as a residue or deposit inthe reaction region. Optionally, one or more mixtures and/or sourcematerials comprises C₃₊. The term “C₃₊” means molecules having at leastthree carbon atoms, including, e.g., coke and soot, whether thoseproducts emerge from the reactor or remain within the pyrolysis reactor.The term “reactor effluent” means products of pyrolysis conducted awayfrom the reactor. The reactor effluent comprises C₂ unsaturates, wherethe term “C₂ unsaturates” means hydrocarbon having two carbon atoms andtwo or four hydrogen atoms. The first, second, third, fourth, and fifthmixtures, and related products and byproducts will now be described inmore detail.

I. First Mixture

In an embodiment, the first mixture comprises hydrocarbon and optionallyfurther comprises molecular hydrogen and/or diluent. The type ofhydrocarbon is not critical; e.g., the hydrocarbon can even compromisehydrocarbon non-volatiles, including those that are not in the gas phaseat the temperature, pressure, and composition conditions subsisting atthe inlet to the pyrolysis reactor. The first mixture's hydrocarbonincludes alkane. The alkane can be, e.g., normal and/or isoalkane,including mixtures thereof. Optionally, the first mixture comprises≧10.0 wt. % alkane based on the weight of the first mixture, e.g., ≧25.0wt. %, such as ≧50.0 wt. %.

In an embodiment, the hydrocarbon is derived from one or more sourcematerials, as defined in the preceding section. The first mixture can bederived from the source material(s) located upstream of the pyrolysis,but this is not required. For example, in one embodiment hydrocarbonderived from a first source material and hydrogen derived from a secondsource material are conducted separately to the pyrolysis reactor, thehydrocarbon and hydrogen being combined to produce the first mixtureproximate to (e.g., within) the pyrolysis reactor. Optionally, thehydrocarbon has (or is derived from one or more source materialshaving), e.g., a hydrogen content in the range of 6.0 wt. % to 25.0 wt.%, 8.0 wt. % to 20.0 wt. % (e.g., not natural gas), or 20.0 wt. % to25.0 wt. % (e.g., natural gas). In a particular embodiment, thehydrocarbon of the first mixture is derived from natural gas (e.g., amethane-containing gas of synthetic and/or geological origin). The firstmixture can comprise, e.g., upgraded natural gas (such as natural gasthat has been sweetened and/or dehydrated). Besides methane, natural gascommonly includes other hydrocarbons (such as ethane and other alkanes),generally in amounts greater than or equal to the amount of methane inthe natural gas on a weight basis. Optionally, the natural gas furthercomprises diluent, e.g., one or more of hydrogen sulfide, nitrogen oroxygenate such as water, CO₂, etc. which can be used as a diluent sourcewhen diluent is present in the first mixture.

Optionally, the first mixture further comprises diluent, e.g., ≧1.0 wt.% of diluent based on the weight of the first mixture. Suitable diluents(which can be a diluent mixture) include one or more of molecularhydrogen, oxygenate, such as water, nitrogen (N₂), hydrogen sulfide, C₄₊mercaptans, amines, mixtures of amines, non-hydrocarbon non-volatiles(whether combustible or not) including refractory inorganics, such asrefractory oxygenates, inert gas (including inert gas mixtures), etc. Inan embodiment, the first mixture comprises ≦10.0 wt. % diluent. When thefirst mixture further comprises a molecular hydrogen diluent, the firstmixture can have a molecular hydrogen to carbon (as all carbon atoms inthe first mixture that are not bound to oxygen atoms, e.g., as can bedetermined by Nuclear Magnetic Resonance Spectroscopy) molar ratio inthe range of from 0.0 to 5.0, e.g., 0.1 to 4.0, such as 1.0 to 3.0 or1.0 to 2.0. Optionally, the first mixture has a hydrogen (all hydrogenatoms in the first mixture regardless of atomic or molecular form) tocarbon (all carbon atoms in the first mixture regardless of atomic ormolecular form) atomic ratio in the range of from 1.0 to 15.0, e.g., inthe range of from 3.0 to 8.0.

In an embodiment, the first mixture comprises a total amount ofnon-combustible non-volatiles (e.g., ash; ASTM D-189), from all sources,≦2.0 parts per million weight (ppmw) based on the weight of the firstmixture, e.g., ≦1.0 ppmw. Optionally, the first mixture comprises atotal amount of combustible non-volatiles (e.g., tar, asphaltenes, ASTMD-6560) in the first mixture, from all sources, ≦5 wt. % based on theweight of the first of the hydrocarbon in the first mixture, e.g., ≦1.0wt. %, such as ≦100.0 ppmw or ≦10.0 ppmw, provided the presence of thecombustible non-volatiles does not result in ≧2.0 ppmw (e.g., ≧1.0 ppmw)based on the weight of the second mixture.

In an embodiment, the first mixture has one or more of the followingproperties: (i) at least 15.0 wt. % of the molecular hydrogen in thefirst mixture (based on the total weight of molecular hydrogen in thefirst mixture) is molecular hydrogen derived from the second mixture orone or more products thereof. In another embodiment, the first mixturecomprises ≧50.0 ppm sulfur based on the weight of the first mixture.

In an embodiment, the first mixture has the following composition: (a)the first mixture comprises (i) ≧10.0 wt. % of hydrocarbon, e.g., ≧25.0wt. % hydrocarbon and (ii) ≧1.0 wt. % molecular hydrogen, e.g., ≧15.0wt. % molecular hydrogen, the weight percents being based on the weightof the first mixture and/or (b) the first mixture comprises (i) ≧0.10mole % of hydrocarbon, e.g., in the range of 0.10 mole % to 90.0 mole %and (ii) ≧0.01 mole % of molecular hydrogen, e.g., in the range of 0.01mole % to 90.0 mole %, the mole percents being per mole of the firstmixture.

II. Second Mixture

In an embodiment, the second mixture comprises ≧1.0 wt. % of unsaturatesand ≧1.0 wt. % of combustible non-volatiles, based on the weight of thesecond mixture. Optionally, the second mixture further comprises one ormore of hydrogen, methane, ethane, or diluent, and optionally furthercomprises benzene, paraffin (iso-, cyclo-, and/or normal) having ≧3carbon atoms, etc.

In an embodiment, ≧90.0 wt. %, e.g., ≧95.0 wt. %, such as ≧99.0 wt. % ofthe second mixture's combustible non-volatiles remain in theregenerative, reverse-flow pyrolysis reactor, e.g., as a deposit in thechannels of the first and/or second reactor, the weight percents beingbased on the weight of the combustible non-volatiles in the secondmixture. In an embodiment, the second mixture has a C₃₊ hydrocarbon:C₂unsaturates weight ratio ≦about 1.0, e.g., ≦about 0.4. Optionally, thesecond mixture has a combustible, non-volatiles:olefin weight ratio≦about 1.0, e.g., ≦about 0.4, such as ≦about 0.1.

In an embodiment, a third mixture is derived from the second mixture inone or more upgrading/treatment stages, e.g., by separating from thesecond mixture one or more of hydrogen, methane, and/or combustiblenon-volatiles. In another embodiment, the third mixture comprises,consists essentially of, or consists of the second mixture, e.g., thatpart of the second mixture which is in the vapor phase at the downstreamend of a regenerative, reverse-flow pyrolysis reactor. For example, athird mixture comprising acetylene can be separated from the secondmixture. If desired, at least a portion of the third mixture's acetylenecan be converted to ethylene, and at least portion of the ethylene canbe polymerized, e.g., to produce polyethylene.

III. Fourth Mixture

The fourth mixture comprises first and second reactants. In anembodiment, the first reactant comprises fuel and the second reactantcomprises oxidant. The fuel and oxidant can be the same as thosedisclosed in U.S. Pat. No. 7,943,808. Optionally, the fuel is derivedfrom, comprises, consists essentially of, or consists of one or more ofhydrogen, CO, methane, methane containing streams, such as coal bedmethane, biogas, associated gas, natural gas and mixtures or componentsthereof, etc. Exothermically reacting the first reactant's fuelcomponent and the second reactant's oxidant component provides at leasta portion of the heat utilized by the pyrolysis, e.g., ≧50%, such as≧75%, or ≧95% of the heat utilized by the pyrolysis. Additional heat,when needed, can be provided to the regenerative, reverse-flow pyrolysisreactor by, e.g., a burner or furnace, e.g., a furnace external to thereactor, but in thermal communication therewith. The first and secondreactants mix within the regenerative, reverse-flow pyrolysis reactor toproduce the fourth mixture, the fuel and oxidant then reacting, e.g., byan oxidation reaction such as combustion, as the fourth mixturetraverses at least a portion of the pyrolysis reactor. The firstreactant comprises fuel, e.g., molecular hydrogen, synthesis gas(mixtures of CO and H₂), or hydrocarbon, such as ≧10.0 wt. % hydrocarbon(including mixtures thereof), or ≧50.0 wt. % hydrocarbon, or ≧90.0 wt. %hydrocarbon based on the weight of the first reactant. The secondreactant comprises oxidant, e.g., molecular oxygen.

The amount of oxidant in the second reactant and the relative amounts offirst and second reactants utilized to produce the fourth mixture can bespecified in terms of the amount of oxidant in the second reactantneeded for oxidizing combustible non-volatiles in the reactor system(“X”) and the amount needed for the substantially stoichiometricoxidation of the first reactant's fuel component (“Y”). In anembodiment, the total amount of oxidant in the fourth mixture is Z(X+Y),wherein Z is in the range of 0.8 to 10.0, e.g., in the range of 1.0 to3.0, and the amounts X and Y are on a molar basis. When Z>1.0, theexcess oxidant can be utilized, e.g., for moderating the reactiontemperature during the oxidation step as disclosed in U.S. Pat. No.7,943,808, and/or for conveying heat within the reactor system. Incertain embodiments, it is desirable for the total flow amount to remainat a relatively constant flow rate over the duration of the oxidationstep's intervals. In such cases the proportion of first or secondreactant flowing in a given interval will be roughly proportional to theduration of that interval (rate×time=amount).

The fourth mixture is generally produced in a mixing region, the mixingregion being located downstream of the first reactor's channels. Thefourth mixture is defined as the combination of the first reactant andsecond reactant. However, at the point at which these streams combine,the combined stream optionally includes species resulting from theoxidation of combustible non-volatiles located in the first reactor'schannels. Optionally, the combined stream further comprises speciesresulting from reaction of the first and second reactants in one or moreof the first reactor's channels, or locations upstream thereof, as aresult of commingling of the first and second reactants. Generally, theamount of commingling is small, as disclosed in U.S. Pat. No. 7,943,808.It can be beneficial for the amount of oxidant in the fourth mixture toexceed that needed to oxidize substantially all of the fourth mixture'sfuel component, e.g., for (i) oxidizing combustible non-volatileslocated in regions of the reactor system downstream of the firstreactor's channels, (ii) moderating the temperature during the oxidationof the fourth mixture's fuel component, and/or (iii) transferring heatwithin regions of the reactor system downstream of the mixing region.The desired amount of excess oxygen can be provided by increasing therelative amount of oxidant in the second reactant and/or by increasingthe relative amount of second reactant in the fourth mixture.

Optionally, the fourth mixture further comprises diluent, e.g., ≧1.0 wt.% of diluent based on the weight of the fourth mixture. Suitablediluents (which can be a diluent mixture) include one or more of, e.g.,oxygenate (water, carbon dioxide, etc.), non-combustible species, suchas molecular nitrogen (N₂), and fuel impurities, such as hydrogensulfide. In an embodiment, the fourth mixture comprises ≦96.0 wt. %diluent, e.g., in the range of 50.0 wt. % to 95.0 wt. % diluent, basedon the weight of the fourth mixture. In an embodiment, diluent isprovided to the fourth mixture as a component of the second reactant.For example, the second reactant can comprise 60.0 mole % to 95.0 mole %diluent and 5.0 mole % to 30.0 mole % oxidant per mole of the secondreactant, such as when the second reactant is air. Optionally, thesecond reactant has a mass ratio of diluent to oxidant in the range of0.5 to 20.0, e.g., in the range of 4.0 to 12.0. It can be beneficial forthe second reactant (and fourth mixture) to further comprise diluent,e.g., for (i) moderating the temperature during the oxidation of thefourth mixture's fuel component and/or transferring heat within thereactor system.

In an embodiment, the first reactant comprises ≧90.0 wt. % molecularhydrogen based on the weight of the first reactant and the secondreactant comprises ≧90.0 wt. % air based on the weight of the secondreactant. When the second reactant comprises >90.0 wt. % air based onthe weight of the second reactant, a fourth mixture produced from thesecan comprise, e.g., ≧1.0 wt. % molecular oxygen, e.g., in the range of5.0 wt. % to 25.0 wt. %, such as 7.0 wt. % to 15.0 wt. %; ≧0.1 wt. %fuel, e.g., in the range of 0.2 wt. % to 5.0 wt. %, the weight percentsbeing based on the weight of the fourth mixture, with the balance of thefourth mixture being molecular nitrogen diluent, e.g., ≧50.0 wt. %diluent, such as in the range of 60.0 wt. % to 94.50 wt. % diluent basedon the weight of the fourth mixture.

IV. Fifth Mixture

The fifth mixture comprises (i) products derived from the exothermicreaction of the fourth mixture's fuel and oxidant with each other andwith the combustible non-volatiles within the reactor, optionally (ii)diluent, when diluent is present in the fourth mixture, and/or (iii)unreacted fuel and oxidant. When the exothermic reaction of the fuel andoxidant involves hydrocarbon combustion, or when a diluent is present inthe fourth mixture (such as N₂ or H₂S), the fifth mixture can comprisecarbon dioxide, and can further comprise sulfur oxides, nitrogen oxides,etc.

A continuous or semi-continuous process for deriving (a) the secondmixture from the first mixture and (b) the fifth mixture from the fourthmixture in a regenerative, reverse-flow reactor system will now bedescribed in more detail. Although the process is described in terms ofa particular regenerative, reverse-flow thermal pyrolysis reactor havingfirst and second reactors the invention is not limited thereto, and thisdescription is not meant to foreclose other embodiments within thebroader scope of the invention.

V. Operation in a Regenerative, Reverse-flow Reactor

One embodiment of the invention is illustrated in FIGS. 1 and 2. Thisembodiment relates to a hydrocarbon conversion system and process,comprising pyrolysing a first mixture comprising hydrocarbon underthermal pyrolysis conditions to produce a second mixture comprisingunsaturated hydrocarbon and combustible non-volatiles. For example, whenthe first mixture comprises methane, the thermal pyrolysis conditionscan include, e.g., exposing the first mixture to a temperature≧1.20×10³° C., e.g., ≧1.40×10³° C., at a total pressure ≧0.1 bar(absolute). The pyrolysis is conducted in a first region 2064 of atleast one regenerative, reverse-flow pyrolysis reactor in pyrolysisstage 206. The process for deriving the second mixture from the firstmixture is generally endothermic, and can be conducted, e.g., under lowor high-severity thermal pyrolysis conditions. The process furthercomprises exothermically reacting in a second region 2063 at least aportion of a second reactant with one or more of (i) a first reactant or(ii) combustible non-volatiles that may be present in stage 206 duringthe oxidation step, the products of (i) and/or (ii) comprising a fifthmixture that can be conducted away.

A particular embodiment is shown in FIG. 3, with plenum 206Bsubstituting for distributor D3. In the embodiment of FIG. 3, theexothermic reaction region 2063 can be located, e.g., between a firstpoint proximate to the downstream end 11 of first reactor 7 and a secondpoint proximate to the downstream end 3 of second reactor 1;“downstream” in this case being with respect to the average flow of thefourth mixture. The pyrolysis region 2064 can be located, e.g., betweena first point proximate to the upstream end 3 of the second reactor 1and a second point proximate to the downstream end 9 of first reactor 7,“upstream” and “downstream” now being with respect to the average flowof the first mixture. It should be appreciated that the invention can bepracticed without precisely defining (a) the boundaries of regions 2063and 2064. Although region 2063 (the exothermic reaction region) is atleast partially coextensive with pyrolysis region 2064, the upstream endof region 2063 (“upstream” with respect to the average flow of thefourth mixture) is generally proximate to the location where asignificant amount of the first and second reactants combine to producean exothermic reaction. The downstream (with respect to the average flowof the first mixture) end of region 2063 is generally proximate to thedownstream end of second reactor 1 as shown in FIG. 3, though this isnot required, and in at least one embodiment the downstream end ofregion 2063 is located further downstream, e.g., in conduit 2066.

The exothermic reacting of the second reactant with (i) the firstreactant and/or (ii) combustible non-volatiles located in stage 206during the oxidation step can provide, e.g., ≧50.0% of the heat utilizedin the first region for deriving the second mixture from the firstmixture. For example, in one embodiment the exothermic reacting of thefourth mixture's fuel and oxidant components provides ≧50.0% of the heatutilized in the first region for deriving the second mixture from thefirst mixture. The first and second regions can be at least partiallycoextensive, for example, and the exothermic reacting of the fourthmixture's fuel and oxidant can be conducted at a substantially differenttime than the pyrolysis. The invention will now be described in terms ofthe high-temperature thermal pyrolysis of a first mixture to produce asecond mixture comprising C₂ unsaturates and combustible non-volatilesin a particular regenerative, reverse-flow thermal pyrolysis reactor.The invention is not limited to this embodiment, and this description isnot meant to foreclose other embodiments within the broader scope of theinvention, e.g., embodiments for producing unsaturated hydrocarbon bysteam cracking and/or alkane (e.g., propane) dehydrogenation.

The first mixture can be derived from one or more source materials 200,e.g., natural gas, petroleum, etc., as described in Section I.Optionally, one or more of the source materials are upgraded in optionalpreparation stage 204 to produce the first mixture. When preparationstage 204 is not utilized, the first mixture can comprise (or consistessentially of, or even consist of) hydrocarbon obtained directly fromsource materials 200, such as natural gas, e.g., with no interveningprocess steps. Following the optional preparation stage 204, the firstmixture is conducted to the pyrolysis stage 206 wherein it is exposed toa temperature ≧1.20×10³° C. under thermal pyrolysis conditions, e.g.,high-severity, thermal pyrolysis conditions, to convert at least aportion of the first mixture to the second mixture comprising ≧1.0 wt. %of unsaturates and ≧1.0 wt. % of combustible non-volatiles based on theweight of the second mixture. A first portion of the second mixture,e.g., a vapor-phase portion which comprises unsaturates, hydrogen, andsaturated hydrocarbon, is conducted away from the pyrolysis stage to anoptional upgrading stage 208 for, e.g., separation of a first separatedportion. A second portion of the second mixture (comprising combustiblenon-volatiles) remains in the stage 206, e.g., as a deposit in thepyrolysis reactor. The first portion:second portion weight ratio is≧1.0, e.g., in the range of 2 to 1000, such as 3 to 100.

The fourth mixture comprises first and second reactants, as specified inSection III. The first reactant can be derived from at least one sourcematerial 300, e.g., natural gas, petroleum, other hydrocarbon, etc.,including fractions, products, or byproducts thereof. The secondreactant can comprise, e.g., oxygen, etc., and can be derived, e.g.,from source material 301, such as air. Optionally, the source materials300 and 301 are upgraded in preparation stages 302 and 303 as shown, toproduce the first and second reactants. The first reactant is conductedto stage 206 via conduit 305, the second reactant being conducted viaconduit 3051. Stages 302 and 303, when used, can produce the first andsecond reactants by one or more of separation, conversion, addition ofrecycled portions of the second and/or fifth mixtures (“EGR”), etc., asdescribed in U.S. Pat. No. 7,943,808.

The process comprises oxidation and pyrolysis steps carried out inpyrolysis stage 206 having at least one regenerative, reverse-flowpyrolysis reactor. Representative reactor systems are illustratedschematically in FIG. 2 and FIG. 3. The reactors are similar, exceptthat the function of distributor D3 in FIG. 2 is performed by plenum206B in FIG. 3. End views of reactor 7 are shown in FIGS. 2A and 3A,with the shaded regions representing the approximate locations ofdistributors D1 and D2, which are utilized to direct reactants into themulti-purpose channels. In both cases, the reactor system comprises atleast one first reactor 7 and at least one second reactor 1. The firstreactor 7 comprises a first multi-purpose channel 14, a secondmulti-purpose channel 15, and a second-reactant channel 16. Channel 14comprises the set of passages identified by the reference number 14 inthe figures. Likewise, channel 15 comprises the set of passagesidentified by the reference number 15 and channel 16 is identified bythe set of passages identified by the reference number 16. The secondreactor 1 comprises at least one passage. The channels of the first andsecond reactor can each comprise one or more passages, e.g., a set ofpassages. In this embodiment, the regenerative, reverse-flow pyrolysisreactor is (i) “reverse flow” in the sense that upstream region of thereactor with respect to the average flow of the first mixture is thedownstream region with respect to the average flow of the fourth mixtureand (ii) “regenerative” in the sense that at least a portion of the heatconsumed during the conversion of the first mixture is provided byexothermically reacting the fourth mixture.

Pyrolysis Step

During the pyrolysis step, valves V1-V4 and V7-V8 are closed. Valves V5and V6 are open. The first mixture is conducted to the first region (thepyrolysis region) 2064 of the regenerative, reverse-flow pyrolysisreactor via at least one conduit 2046. The second mixture, derived fromthe first mixture by the pyrolysis, is conducted away from region 2064via at least one conduit 2065. The reactor optionally includes means fordirecting the first mixture from conduit 2046 into the passages of thesecond reactor 1, e.g., plenum 206A and means (such as plenum 206B) fordirecting at least a portion of the second mixture, e.g., the portion inthe vapor phase, to conduit 2065.

In the illustrative embodiment, regions 2063 and 2064 are at leastpartially coextensive as shown in FIG. 1. Region 2063 encompasses atleast the second reactor. Region 2064 encompasses at least a portion ofeach of the first and second reactors. At least a portion of the heatproduced in region 2063 during the exothermic reaction of the fourthmixture during the first and second intervals of the oxidation step isused to provide at least a portion of the heat utilized in region 2064for the endothermic pyrolysis step. Optionally, a major amount(e.g., >50%) of the heat abstraction occurs in the portion of region2064 that is coextensive with region 2063.

In an embodiment, the pyrolysis is a high severity pyrolysis and thesecond mixture comprises acetylene that can be converted, e.g., toethylene. For example, a third mixture can be derived from at least aportion of the second mixture in optional upgrading stage 208, with thethird mixture being conducted via at least one conduit 2086 to aconversion stage 210, for converting at least a portion of the thirdmixture's acetylene to a first product comprising, e.g., one or more ofethylene, ethylene glycol, acetic acid, acrylic acid, benzene, toluene,or xylene, styrene, or butadiene. Polymerizing at least a portion of thefirst product, e.g., to produce polyethylene, is within the scope of theinvention.

In one embodiment, stage 208 includes upgrading means, e.g., means forremoving from the second mixture one or more of hydrocarbon (such assaturated hydrocarbon and/or those containing one or more heteroatoms),diluent, non-volatiles, and hydrogen, etc. For example, stage 208 caninclude one or more of a tar and/or solid removal means, compressionmeans, adsorption means, distillation means, washing means, or dryingmeans. While stage 208 can encompass conventional processing, e.g.,conventional separation means, such as those described in U.S. Pat. No.7,943,808, the invention is not limited thereto. Separation means can beused, e.g., for removing from the second mixture one or more ofcondensable species (e.g., condensable hydrocarbon); light-gas (e.g.,one or more of hydrogen, light saturated hydrocarbon such as methane,carbon dioxide, hydrogen sulfide, etc.); or water.

Stage 208 can include, e.g., means for cooling and then compressing thesecond mixture conducted away from stage 206. For example, inembodiments where stage 206 has an outlet pressure<the inlet pressure ofthe converter of stage 210, stage 208 can include, e.g., compressing atleast the portion of the second mixture from which the third mixture isderived in order to achieve the desired stage 210 inlet pressure. Shouldthe second mixture comprise acid gases (e.g., CO₂ and/or H₂S), these canbe removed, e.g., downstream of the compression—a desirable locationsince the gas volume has been reduced significantly during compression.Conventional methods are suitable for removing acid gases, e.g., caustictreatment, but the invention is not limited thereto. Acid gasesseparated from the second mixture can be conducted away, e.g., forstorage or further processing such as in a Claus plant.

In an embodiment, at least a portion of any hydrogen, saturatedhydrocarbon, diluent, etc., separated from unsaturates in upgradingstage 208 are recycled, e.g., by combining such separated species withone or more of the first mixture's source materials, e.g., inpreparation stage 204. The pyrolysis will now be described in moredetail.

Although the invention is not limited thereto, conventional pyrolysisreactors can be adapted for use in stage 206. Suitable reactors include,for example, regenerative reverse flow reactors as described in U.S.Patent App. Pub. No. 2007/0191664 and thermal pyrolysis reactors asdescribed in U.S. Pat. No. 7,491,250; U.S. patent application Ser. No.61/349,464; and U.S. Patent App. Pub. Nos. 2007/0144940 and2008/0142409, all of which are incorporated by reference herein in theirentirety. In an embodiment, the thermal pyrolysis is conducted underhigh-severity thermal pyrolysis conditions, e.g., by exposing the firstmixture to temperature in the range of about 1.40×10³° C. to about2.30×10³° C., e.g., in the range of about 1.45×10³° C. to about1.80×10³° C. Optionally, ≧25.0 wt. % (such as of the ≧50.0 wt. %or >75.0 wt. %) of the first mixture achieves a peak pyrolysis gastemperature ≧1.40×10³° C., e.g., in the range of about 1.50×10³° C. toabout 1.675×10³° C., based on the weight of the first mixture.

Although the process is robust and can operate within a wide range ofpyrolysis conditions, e.g., temperature, pressure, residence times,severity, etc., the conditions are generally selected to increase therelative amount of C₂ unsaturates in the second mixture, e.g., toincrease the acetylene to combustible non-volatiles weight ratio.Relatively long residence times can result in over-cracking of the feedmolecules, leading to an undesirable increase in the amount of methaneand/or combustible non-volatiles in the second mixture. In anembodiment, residence time is ≦about 0.3 seconds, e.g., ≦0.05 seconds.In an embodiment, the pyrolysis is high-severity, thermal pyrolysis andthe residence time is ≦0.05 seconds, such as ≦0.02 seconds. Residencetime can be selected, e.g., for optimum unsaturates' yield underpyrolysis conditions. This can be done by measuring the amount ofunsaturates in the second mixture under substantially constant thermalpyrolysis conditions at a plurality of residence times. The optimumresidence time can be approximated using conventional interpolation andextrapolation of the measured values. The optimum residence time canalso be approximated using pyrolysis reaction simulations of secondmixture composition as a function of pyrolysis conditions and residencetime, including conventional pyrolysis reaction simulations.

In an embodiment, the pyrolysis is conducted for a time duration (t₁)sufficient for exposing ≧50.0 wt. %, e.g., ≧75.0 wt. %, such as ≧90.0wt. % of the first mixture (based on the weight of the first mixture) topyrolysis conditions for a residence time ≦about 0.3 seconds, e.g.,≦0.05 seconds. In an embodiment, t₁ is ≦10.0 seconds, e.g., ≦5.0seconds, such as ≦1.0 seconds. Optionally, t₁ is in the range of 0.1seconds to 100.0 seconds, e.g., 1 to 30 seconds.

Oxidation Step

During the first interval of the oxidation step, valves V8, V7, V2 andV4 are open. Valves V1, V3, V5, and V6 are closed. The first reactant isconducted through at least one conduit 305 and to at least one firstdistributor (D1), wherein D1 directs the flow of the fuel into channel14 within first reactor 7. A first portion of the second reactant isconducted through at least one conduit 3051 and to at least one seconddistributor (D2), wherein D2 directs the flow of the first portion ofthe second reactant to channel 15 within first reactor 7. A secondportion of the second reactant is conducted to the first reactor fromconduit 3051, optionally through third distributor D3 (as shown in FIG.2), which directs the flow of the second portion into channel 16 withinthe first reactor. The first reactant, first portion of the secondreactant, and second portion of the second reactant generally combine inregion 13 to produce the fourth mixture (for the exothermic reaction) inproximity to the downstream end of first reactor 7, which in thisembodiment defines the upstream end of an exothermic reaction region2063. For the description of the oxidation step, upstream and downstreamare defined with respect to the average flow of the fourth mixture, andcomponents and products thereof. Oxidant conducted through channels 15and 16 and passages in the second reactor during the first intervalreacts with the combustible non-volatiles deposited therein duringpreceding pyrolysis steps, thereby lessening the amount of accumulatedcombustible non-volatiles. A fifth mixture is directed by plenum 206A toat least one conduit (2066), and conducted away from the regenerative,reverse-flow pyrolysis reactor, the fifth mixture comprising at least aportion of the compositions resulting from the reaction of the fourthmixture's fuel and oxidant, compositions resulting from the oxidation ofcombustible non-volatiles in stage 206, and optionally at least aportion of any fourth mixture that is not consumed in the reaction.

During the second interval of the oxidation step, valves V2, V4, V5, andV6 are closed. Valves V7, V8, V1, and V3 are open. The first reactant isconducted through at least one conduit 305 to optional seconddistributor D2, wherein D2 now directs the flow of the first reactantinto channel 15 within first reactor 7. A first portion of the secondreactant is conducted through at least one conduit 3051 to firstdistributor D1, wherein D1 now directs the flow of the first portion tochannel 14 within first reactor 7. A second portion of the secondreactant is conducted to the first reactor from conduit 3051, optionallythrough third distributor D3 (or plenum 206B as shown in FIG. 3) whichdirects the flow of the second portion into channel 16 within the firstreactor. As in the first interval, the first reactant, first portion ofthe second reactant, and second portion of the second reactant generallycombine in region 13 to produce the fourth mixture in proximity to thedownstream end of first reactor 7. The fifth mixture is conducted awayin the same as in the first interval. Oxidant conducted through channels14 and 16 (and through passages of the second reactor) during the secondinterval reacts with the combustible non-volatiles deposited thereinduring preceding pyrolysis steps, thereby lessening the amount ofaccumulated combustible non-volatiles.

In an embodiment, ≧50.0 wt. %, e.g., ≧75.0 wt. %, such as ≧95.0 wt. % ofthe combustible non-volatiles in passages of the first and secondreactors (e.g., channels 14, 15, and 16) are removed during theoxidation step, the weight percents being based on the weight of theaccumulated combustible non-volatiles in the channels at the start ofthe second interval.

During all intervals of the oxidation step, it can be desirable to havecomparable pressure drop (ΔP) across the length of the passages includedin the first reactor (from fuel/oxidant inlet to mixer outlet, e.g.,from face 9 to face 11 in FIG. 3). Comparable ΔP provides pressures ineach passage that are similar to the pressures in neighboring passages,and thus limits the driving force for fuel and oxidant mixing prior toreaching the mixer end 11. Limiting fuel/air mixing upstream of region13 leads to an increase in the amount of oxidation occurring in mixerregion 13, which increases the selectivity and energy efficiency of thereactor system. Accordingly, in one embodiment, the relative number ofpassages constituting channels 14, 15, and 16 during a particularinterval of the oxidation step is set to achieve approximately equal ΔPacross the length of each passage in the first reactor. For example,during the first interval, the first reactant is carried by the firstmulti-purpose channel 14 and the second reactant is carried by thecombination of second multi-purpose channel 15 and the second-reactantchannel 16. The ratio of (i) the number of passages constituting thefirst multi-purpose channel to (ii) the number of passages constitutingthe second multipurpose channel and the second-reactant channel isselected so that that ΔP is substantially the same for all channels.

Conventional methods can be used for determining ΔP and for designing areactor having channels of substantially equal ΔP, using, e.g.,parameters such as passage dimensions, gas viscosity, gas velocity, etc.Conventional methods can be utilized for determining the proportion ofpassages needed to carry the fuel and oxidant in order to achievesimilar ΔP, using, e.g., the relative flow rates of fuel and oxidant.The relative number of passages in each channel in each interval is mosteasily understood when the passages are all of equal dimension (as inhoneycomb monoliths). However, the invention is not limited to suchgeometries, and may be applied to other structured or random packingcreating constant or variable passage dimensions.

In many practical embodiments, the proportion of passages of the firstreactor utilized for carrying fuel is much less than the proportion forcarrying oxidant. For example, in a stoichiometric reaction of methanefuel with air oxidant, approximately 10 moles of methane react withapproximately 100 moles of air. In an embodiment where (i) all passageshave similar dimensions and (ii) the fuel and air have substantiallysimilar gas properties (e.g., viscosity), approximately 10/110 (or about9%) of the first reactor's passages are used to carry fuel at comparableΔP with those carrying air. In other embodiments, the fuel passage:airpassage number ratio (by number) is <0.09. For example, in embodimentswhere the fuel comprises ≧90.0 wt. % methane based on the weight of thefuel, the fuel passages can transport more moles of fuel at comparableΔP to the air passages because methane has a lower viscosity than air.Other embodiments, e.g., those where the flow rate of oxidant-carryingstream is increased by addition of diluent or by the choice to operatewith excess oxidant, utilize a further increase in the proportion ofpassages carrying oxidant during the oxidation step. Other embodiments,e.g., those where the flow rate of fuel-carrying stream is increased byaddition of diluents or by the choice to operate with excess fuel,utilize an increase in the proportion of passages carrying fuel duringthe oxidation step. In an embodiment, the oxidation step is conductedfor a time duration (t₂) sufficient for the second reactor to abstractsufficient heat from the oxidation to accomplish the pyrolysis step. Thevalue of t₂ depends on factors, such as the geometry of the reactorsutilized in stage 206, the heat transfer characteristics of the reactorsand the materials from which the reactors are made, and the amount ofheat needed by the pyrolysis step. Generally, the oxidation step isconducted for a time duration greater than or equal to a time sufficientfor heating the pyrolysis region 2063 for exposing ≧50.0 wt. % of thefirst mixture, e.g., ≧75.0 wt. %, such as ≧90.0 wt. % to a temperaturesufficient for thermally pyrolysing the first mixture to produce thedesired second mixture; the weight percents being based on the weight ofthe first mixture. In an embodiment, t₂ is ≦10.0 seconds, e.g., ≦5.0seconds, such as ≦1.0 seconds. Optionally, t₂ is in the range of 0.1seconds to 100.0 seconds, e.g., in the range of 1.0 to 30.0 seconds.

Generally, the time duration of the oxidation step's first interval isselected for a time sufficient to remove ≧50.0 wt. %, e.g., ≧75.0 wt. %,such as ≧90.0 wt. %, of the combustible non-volatiles accumulated inchannel 15 over a sequence of preceding pyrolysis steps. The weightpercents are based on the total weight of combustible non-volatilesaccumulated in channel 15 over a sequence of preceding pyrolysisstep(s). Likewise, the time duration of second interval is selected fora time sufficient to remove ≧50.0 wt. %, e.g., ≧75.0 wt. %, such as≧90.0 wt. %, of the combustible non-volatiles accumulated in channel 14over a sequence preceding pyrolysis step(s). The weight percents arebased on the total weight of combustible non-volatiles accumulated inchannel 14 over a sequence of preceding pyrolysis step(s). The oxidationstep can comprise the first and second interval only, but the inventionis not limited thereto. In an embodiment, the first interval and secondinterval are repeated in sequence, one after the other, with nointervening pyrolysis step, until the desired time duration for theoxidation step is achieved. Such an embodiment can be beneficial whenthe second mixture contains a significant amount of combustiblenon-volatiles, which are deposited in the first reactor's channels. Inan embodiment having a first reactor comprising two multi-purposechannels, the time duration of the first interval t_(2a) issubstantially equal to the time duration of the second interval t_(2b).The term “substantially equal” in this context means t_(2b) is within+/−20%, e.g. within +/−10% of t_(2a). In the case where the oxidationstep comprises a plurality of first intervals and at least one secondinterval, Σt_(2a): Σt_(2b) can be substantially equal; where Σt_(2a)represents the sum of the time durations of all first intervals in asingle oxidation step and Σt_(2b) represents the sum of the timedurations of all second intervals in a single oxidation step. The timeduration of a single oxidation step t₂ is generally ≧Σt_(2a)+Σt_(2b).For example, when there is substantially no dead time in switchingvalves v1-v4 from the first interval to the second, and when no purgefluid (e.g., a sweep gas) is utilized between the first and secondintervals, t₂ is substantially equal to Σt_(2a)+Σt_(2b). WhenΣt_(2a)+Σt_(2b) is less than the amount of time needed for the secondreactor to abstract sufficient heat from the oxidation to accomplish thepyrolysis step, oxidation of the fourth mixture can continue (e.g., asadditional first and/or second intervals) until the reactor abstracts asufficient amount of heat. In other words, the oxidation step cancontinue beyond the time duration needed to lessen the amount ofdeposits of combustible, non-volatile deposits in the pyrolysis reactor,e.g., when additional time is needed to heat the reactor for thepyrolysis step. For other embodiments, e.g., having a first reactorcomprising >2 multi-purpose channels, time intervals can be determinedutilizing the following guidelines: (i) the amount of reactant thatflows through each multipurpose channel over all the intervals in theoxidation step should be substantially equal and (ii) the total time(over all the intervals in the oxidation step) that second reactantflows in each multipurpose channel should be sufficient to remove ≧90.0wt. % of the combustible non-volatiles present in the multipurposechannel at the start of the oxidation step. In other embodiments, e.g.,those having a first reactor having one multi-purpose channel (e.g., theembodiment of FIG. 5), the duration of t_(2b) is generally within+/−20%, e.g. within +/−10% of the time needed to remove ≧90.0 wt. % ofthe combustible non-volatiles present in the multi-purpose channel atthe start of the second interval.

After at least a portion of the fifth mixture is conducted away fromregion 2063, the first mixture is again conducted to region 2064, andthe process repeats in sequence—exothermically reacting the fuel andoxidant of the fourth mixture to heat the reactor and then utilizing atleast a portion of the heat for pyrolysing the first mixture. The firstand second intervals of the oxidation step can be operated in sequence,one after the other, or alternatively, the first interval of theoxidation step can be followed by the pyrolysis step, the pyrolysis stepthen being followed by the second interval of the oxidation step.

The process can be operated sequentially, e.g., continuously,semi-continuously, or even in batch mode. In an embodiment, stage 206comprises a plurality of pyrolysis reactors operating, e.g., in series,parallel, or a combination thereof, with at least one pyrolysis reactorhaving (i) pyrolysis step(s) and (ii) oxidation step(s) having thedescribed first and second intervals. When stage 206 comprises aplurality of pyrolysis reactors, the sequence of oxidation steps andpyrolysis steps in each reactor can be out of phase, e.g., to provide acontinuous flow of second mixture from the process. For example, in oneembodiment stage 206 can comprise two reactor systems R1 and R2operating in parallel. In this embodiment, the second mixture can beobtained from R1 undergoing a pyrolysis step while R2 is undergoing anoxidation step in a first period, and then in a second period, thesecond mixture is obtained from R2 undergoing a pyrolysis step while R1is undergoing an oxidation step.

Although the process is described in terms of an embodiment utilizingvalve means, e.g., mechanical valves such as poppet valves, ball valves,gate valves, etc., for directing the flow of the first reactant (viaconduit 305) and the second reactant (via conduit 3051) into theappropriate channels of the first reactor 7 during the first and secondintervals of the oxidation step, the invention is not limited thereto,and this description is not meant to foreclose other embodiments withinthe broader scope of the invention. For example, in another embodiment,reactor system 206 includes one or more movable (e.g., rotating ortranslating) vanes or spargers situated upstream of a stationary (withrespect to the rotation of the vanes or spargers) first reactor 7.During the oxidation step, such vanes and/or spargers direct acontinuous flow of first and second reactant into the passages of thereactor interfacing with the moving vanes or spargers. The spargermotion results in a changing proximity between sparger and passages. Forexample, a sparger associated with conduit 305 directs first reactantinto the passages proximate to the sparger. As the sparger moves awayfrom a passage, that passage is no longer proximate to the sparger, andmay receive flow of second reactant via plenum 206B. In this embodiment,the multipurpose channel is comprised of all the reactor passages thatare proximate to a moving sparger at any time during an oxidation step.Second-reactant passages are those passages that are not proximate to amoving sparger at any time during an oxidation step.

In yet another embodiment, typically stationary vanes and/or spargerscan be used in combination with a moving (e.g., rotating) reactor 7(e.g., a Ljungström geometry having (i) a rotating reactor or (ii) afixed reactor with moving vanes). For example, reactor 7 can be in theform of an elongated cylinder having, e.g., a circular cross-section,with a rotational axis parallel to the reactor's axis of cylindricalsymmetry. During the oxidation step, the motion of the sparger relativeto that of the reactor has the same effect as the motion of the reactorrelative to that of the sparger; that is, it creates a constantlychanging proximity between sparger and passages resulting in a set ofmultipurpose passages. Optionally, the rotating reactor system 206further comprises additional flow control means, e.g., additional vanes,which can be for (i) directing the flow of the first and/or secondmixture into channels of first reactor 7 and (ii) for directing at leasta portion of the second mixture toward conduit 2065, the average flow ofthe first and second mixtures being countercurrent to the direction ofthe fourth mixture's average flow. Optionally, the first 7 and second 1reactors have a common axis of cylindrical symmetry with the secondreactor rotating about such axis in synchronization with the rotation ofthe first reactor and/or the flow-control means. One benefit of therotating reactor is that the rotating reactor(s) and/or vanes can beoperated to permit the simultaneous operation of (i) the pyrolysis stepand (ii) the first and second intervals of the oxidation stepcontinuously within stage 206, with the average flow of the first andsecond mixtures being countercurrent to the average flow of the fourthand fifth mixtures. Motor means can be used to drive the rotationalmotions utilized in these embodiments. Such motor means can be (a)external to stage 206, e.g., as in the case of an electric motor andassociated transmission of rotational energy, or (b) derived in partfrom hydrodynamic forces in stage 206. When the first reactor is amoving (e.g., rotating) reactor utilized in combination with fixedand/or movable flow control means utilized to direct the flow of thefirst and second reactants into the first reactor's channels, therelationship between the reactor's passages and channels changes frominterval-to-interval of the oxidation step. In other words, thesequencing of first and second reactant during the intervals of theoxidation step depends on the relative motion of (i) the flow controlmeans and (ii) the reactor's passages. In such embodiments, the movingreactor comprises at least one multi-purpose channel, the multi-purposechannel comprising a passage or set of passages fed by the firstreactant during at least one first interval of the oxidation step andwhich are fed by the second reactant during at least one second intervalof the oxidation step, the second interval occurring before or after thefirst interval. The reactor can, e.g., further comprise asecond-reactant channel, comprising a set of passages that do not conveythe first reactant during any interval of the oxidation step.

When valve means are utilized to direct the flow of the first, second,fourth, and fifth mixtures, at least some of the valve means can behydrodynamic valve means. For example, in an embodiment illustrated inFIG. 4 and FIG. 5, the function of valves V1 and V2 are executed by thehydrodynamics of the reactor and distributor design, and a single valveV8 controls the flow of all of the second reactant (first and secondportions). In such embodiments, distributor D1 is configured for (i)directing the flow of the first reactant to channel 14 when flow of thefirst reactant emerges from D1 (during the first interval) and (ii)directing the flow of the first portion of the second reactant around D1via flow-path 20 toward channel 14 when the flow of first reactant doesnot emerge from D1 (during the second interval), as a result ofhydrodynamic forces present in the reactor and D1. The second portion ofthe second reactant flows from distributor D3 (or alternatively viaplenum 206B) toward channel 16 during the first and second intervals. Itcan be advantageous to utilize hydrodynamic valving when the firstreactor 7 comprises sections as described in more detail below inconnection with the high temperature thermal pyrolysis of hydrocarbon.The use of hydrodynamic valving, reactor sections, etc., is not limitedto embodiments utilizing a high-temperature thermal pyrolysis ofhydrocarbon.

Optionally, the process further includes one or more of the followingcomponents: treating/upgrading stage 308 for treating and/or upgradingthe fifth mixture downstream of conduit 2066; one or more conduits foradding to the fourth mixture's fuel source material 300; one or more ofmolecular hydrogen and/or light saturated hydrocarbon, such as methane3001 or diluent, such as oxygenate 3002; conduits for adding to thefourth mixture's oxidant source material 301 additional or supplementaloxidant 3003 or diluent 3004; one or more conduits for adding to thefirst source material one or more of molecular hydrogen 2043,hydrocarbon, e.g., light saturated hydrocarbon such as methane 2044, ordiluent, such as oxygenate 2045; one or more conduits for conductingaway heteroatom species, such as hydrogen sulfide or non-volatiles 2041;one or more conduits for conducting away a first byproduct fromupgrading stage 308, the first byproduct including at least one ofnon-oxidized hydrocarbon 3081 and/or, diluent such as oxygenate 3082; aconduit 3083 for conducting heteroatom species such as NO_(x), SO_(x),CO₂, N₂, sulfuric acid, etc., away from upgrading stage 308; one or moreconduits for conducting a second byproduct away from stage 208, thesecond byproduct including, e.g., one or more of molecular hydrogen 2082or light saturated hydrocarbon 2083; one or more conduits for conductingaway non-volatiles 2084 and/or heteroatom species, such as hydrogensulfide 2085 away from upgrading stage 208; or one or more conduits (notshown) for adding to the second mixture one or more of (i) hydrogen;(ii) methane, ethane, and/or other light saturated hydrocarbon; or (iii)ethylene.

One embodiment of the process will now be described in more detail withreference to the reactor system shown schematically in FIG. 4. In thisembodiment, the first interval of the oxidation step, the secondinterval of the oxidation step, and the pyrolysis step are operatedcontinuously in sequence. This description is not meant to forecloseother embodiments within the broader scope of the invention, such asthose which, e.g., (i) utilize more than one pyrolysis reactor, (ii)have a pyrolysis step between the first and second intervals of theoxidation step, have additional oxidation intervals whether in sequenceor otherwise, or (iii) are not operated continuously.

VI. Continuous Process Utilizing Hydrodynamic Valving

In one embodiment, the invention relates to a continuous process forconverting a first mixture comprising hydrocarbon to a second mixturecomprising ≧1.0 wt. % C₂ unsaturates and ≧1.0 wt. % combustible,non-volatiles (based on the weight of the second mixture) by exposingthe first mixture to a temperature ≧1.20×10³° C. under thermal pyrolysisconditions in a pyrolysis region of a regenerative, reverse-flow thermalpyrolysis reactor. At least a portion of the heat utilized by thepyrolysis is provided by providing a fourth mixture comprising first andsecond reactants to an oxidation region of the regenerative,reverse-flow thermal pyrolysis reactor, and oxidizing the firstreactant's fuel component. The relative amounts of the first and secondreactants; the types and amounts of fuel in the first reactant; thetypes, locations, and amounts of combustible non-volatiles present instage 206 during the oxidation step; and the types and amount of oxidantin the second reactant are selected so that the (exothermic) heat ofreaction obtained during the oxidation step sufficiently heats thepyrolysis region, particularly the portion of the pyrolysis region thatis coextensive with the oxidation region, for exposing the first mixtureto a temperature ≧1.20×10³° C., e.g., ≧1.40×10³° C., and lessens theaccumulation of combustible non-volatiles. In this embodiment, theoxidation step comprises first and second intervals, the first andsecond intervals having no intervening pyrolysis step.

In this embodiment, pyrolysis stage 206 utilizes hydrodynamic valvingand at least one regenerative-reverse-flow thermal pyrolysis reactorsystem as illustrated schematically in FIG. 4. Stage 206 comprises tworeactors: a first (recuperator/quenching) reactor 7 and a second(pyrolysis/reforming) reactor 1, the first reactor 7 comprising (i) amulti-purpose channel 14 and (ii) a second-reactant channel 16, which isutilized for conducting a portion of the second reactant during thefirst and second intervals.

The first and second reactors comprise regenerative beds, theregenerative beds comprising bedding or packing material, such as one ormore of glass or ceramic beads or spheres; metal beads or spheres; (i)ceramic, including, e.g., alumina, silica, yttria, zirconia, etc., andmixtures thereof; or (ii) metal honeycomb materials; ceramic tubes;extruded monoliths catalysts; etc. The materials comprising theregenerative bed are selected to maintain integrity, functionality, andwithstand long term exposure to temperatures ≧700° C., e.g., ≧1200° C.,such as ≧1500° C., or even ≧2000° C. for operating margin. The first andsecond reactors can be, e.g., the same as those described in U.S. Pat.No. 7,943,808. The shape of the regenerative beds is not restricted toany particular geometry. For example, the first and second reactors canbe elongated, and can have elliptical, cylindrical, and/or rectangularcross-sections, including combinations thereof. The reactors can be ofthe same shape and size, but this is not required. For example, thefirst reactor can be in the form of a honeycomb monolith ofsubstantially cylindrical cross-sections. The first reactor's channelseach comprise a plurality of passages, the passages comprisingsubstantially parallel, substantially independent flow-paths within theregenerative media, e.g. within the honeycomb. The passages can each beof the same size, shape, and ΔP, for example. Channel 14 comprises theset of passages whose entrance interfaces with (e.g., are proximate to)distributor D1, as identified by the reference number 14 in FIG. 5.Channel 16 comprises the set of passages whose entrance interfaces with(e.g., are proximate to) distributor D3 identified by the referencenumber 16 on FIG. 5. The scale of FIG. 4 does not permit perfectrepresentation of the relationship between passages and distributors.However, channel 14 generally comprises the passages proximate to thedistributor D1, while channel 16 generally comprises all other channelsthat are accessible to plenum 206B, as shown in FIG. 4A for a spargerhaving a cylindrical geometry.

In an embodiment, ≧50.0 wt. %, e.g., ≧75.0 wt. %, such as ≧90.0 wt. % ofthe second reactant is conducted to region 2063 by channel 16 during thefirst interval of the oxidation step and by the channels 14 and 16during the second interval, the weight percent being based on the totalweight of the second reactant. Optionally, the first reactor 7 furthercomprises means for supplying additional fuel to region 2063, e.g., by afirst-reactant conduit (not shown) external to first reactor 7 and/or afirst-reactant channel (not shown) located within first reactor 7.Optionally, such means are utilized solely for conducting the additionalfuel (as, e.g., first reactant) toward region 2063. The invention iscompatible with this use of such first-reactant channels, and optionallyfor conducting the first and/or second mixture away from region 2064during the pyrolysis step, though it can be undesirable to do so. Forexample, combustible non-volatiles can accumulate in such first-reactantchannels as a result of deposits formed as a result of (i) the pyrolysissteps or (ii) the oxidation step for fuels a tendency to form depositssuch as coke. The accumulation of such deposits in the first-reactantchannel is not diminished during the oxidation step because the secondreactant is generally excluded from the first-reactant channels. In anembodiment, ≧50.0 wt. %, e.g., ≧75.0 wt. %, such as ≧90.0 wt. % of thefirst reactant is conducted to region 2063 by channel 14 during thefirst interval of the oxidation step, the weight percents being based onthe total weight of the first reactant.

Optionally, one or more mixer means are used between the first andsecond reactors to improve the oxidation reaction. Mixer means,distributor means, reactor system internals, flow-control means, etc.,for the reactor system included in stage 206 can be substantially thesame as those described in U.S. Pat. No. 7,943,808, for example.

It is understood that flow control means (e.g., one or more of valves,rotating reactor beds, check valves, louvers, flow restrictors, timingsystems, etc.) can be used to control gas flow, actuation, timing, andto alternate physical beds between the flow systems for the first,second, fourth, and fifth mixtures, and the optional purge gas whenused. For example, stage 206 can further comprise means for conveyingfuel (via conduit 305) and oxidant (via conduit 3051) into theappropriate channels in the first reactor. Such means can include, e.g.,one or more of plenums, valves, vanes, spargers and/or distributors.Suitable spargers, distributors, etc., are disclosed in U.S. Pat. No.7,815,873; which is incorporated by reference herein in its entirety.Although the invention is compatible with the use of conventionalspargers, distributors, plenums, etc, in stage 206, the invention is notlimited thereto.

The oxidation step will now be described in more detail.

Oxidation Step

The oxidation step begins by conducting first and second reactants tothe first reactor 7. The first reactant is conducted to first reactor 7via conduit 305. The second reactant is conducted to the first reactorby conduit 3051, optionally substantially simultaneously with theconduction of the fuel in conduit 305. In the embodiment illustrated inFIG. 4, the first and second reactants do not mix appreciably upstreamof end 11 of first reactor 7, e.g., ≧80.0% of the mixing of the firstand second reactants by weight, such as ≧90.0%, occurs downstream of end11 of first reactor 7. The invention is not limited to this embodiment,and this description is not meant to foreclose other embodiments withinthe broader scope of the invention, such as embodiments where there is asignificant amount of fuel and oxidant mixing in the first reactor.Continuing with the embodiment illustrated in FIG. 4, proximate to thedownstream end 11 of the first reactor 7, the first and second reactantscombine to produce a fourth mixture. The fuel and oxidant of the fourthmixture react exothermically at or proximate to a central region 13 ofthe reactor system. Optionally, the exothermic reaction continuesdownstream (with respect to the average flow of the fourth mixture) ofregion 13, e.g., in second reactor 1. The fifth mixture is conductedaway from second reactor 1 via one or more conduits 2066. The oxidationstep can result in a high temperature zone (also referred to by thoseskilled in the art as a temperature bubble), at least a portion of thetemperature bubble being located in region 2063. The temperature bubbleis illustrated schematically as a Gaussian-like shape in FIG. 4.

The oxidation step thus includes the following features: (i) heating ofregion 13 and the second reactor 1 by transferring at least a portion ofthe heat of combustion to the reactor system downstream of the end 11 ofthe first reactor 7 and (ii) by transferring at least a portion of thesensible heat recovered by the first and second reactants in an upstreamregion of the first reactor (upstream with respect to the flow of thefirst and second reactants) toward one or more of the downstream regionof the first reactor, region 13, or the second reactor in order tothermally regenerate the reactor system. Accordingly, at least a segmentof each of the right-hand and left-hand edges the temperature profiletranslate downstream from their starting locations at the beginning ofthe oxidation step, as shown in FIG. 4 by arrows 6 and 8. It should berecognized that the translations indicated by arrows 2, 4, 6, and 8 ofthe temperature profile's edges during the oxidation and pyrolysis stepsconfines the temperature profile (which can achieve temperaturese.g., >1600° C.) to regions of the reactor system that can tolerate suchconditions long-term. Optionally, the shift in the edges of thetemperature profile is accompanied by a shift in the position of thepeak of the temperature profile. Operating conditions during theoxidation step can be substantially the same as those disclosed in U.S.Pat. No. 7,943,808. In an embodiment, the exothermic reaction of thefuel and oxidant components of the fourth mixture includes combustion,the combustion conditions including a temperature ≧1.40×10³° C., e.g.,≧1.50×10³° C., such as ≧1.60×10³° C., e.g., in the range of 1.90×10³° C.to 2.20×10³° C., and a pressure ≧1.0 bar (absolute), e.g., in the rangeof 1.0 bar to 15.0 bar, such as 2.0 bar to 5.0 bar.

Optionally, the oxidation step oxidizes ≧90.0 wt. % of the firstreactant's fuel component e.g., ≧99.0 wt., % based on the weight of thefirst reactant's fuel component. Optionally, diluent, such as nitrogen,that may be present in the fourth mixture is not oxidized to asignificant extent. Optionally, ≧50.0% of the oxidation of the fourthmixture (based on the amount of the fourth mixture, mole basis, that isoxidized in region 2063), e.g., ≧75.0%, such as ≧90.0% of the oxidationoccurs in the portion of region 2063 that is located between the firstand second reactors.

In this embodiment, the total duration of an oxidation step t₂ is for atime sufficient for the second reactor to abstract sufficient heat fromthe oxidation to accomplish the pyrolysis step. In other words, theoxidation step is conducted for a time duration greater than or equal toa time sufficient to displace the peak of the temperature toward thesecond reactor sufficient to heat the pyrolysis region 2064 for exposingthe first mixture to a temperature ≧1.20×10³° C. during the pyrolysisstep. Optionally, t₂ is in the range of 0.1 seconds to 30.0 seconds.Optionally, the total amount of heat added to the reactor system duringthe oxidation step (also called the “regeneration” step) does not exceedthe sum of the heats that are required (a) to sustain the pyrolysisreaction for endothermically driving the second mixture from thepyrolysis portion of the first mixture and (b) for heat losses from thesystem, e.g., by as conduction losses through reactor walls and/orconvective losses with, e.g., the second mixture. Optionally, the totalamount of heat stored in the reactor system is generally much more thanthe minimum amount of heat needed for the pyrolysis step.

In order to lessen the accumulation of deposits, such as combustiblenon-volatiles (e.g., coke) in stage 206, particularly those present inthe passages of first reactor 7, the oxidation step is divided intofirst and second intervals, which will now be described in more detail.

Oxidation Step—First Interval

Referring to FIG. 4, valves V8, V7, and V4 are open during the firstinterval of the oxidation step and valves V5 and V6 are closed. Thefirst reactant is conducted through conduit 305 to first distributor D1,which directs the flow of the first reactant into channel 14 withinfirst reactor 7. An end-view of reactor 7, illustrating the approximatelocation of distributor D1 (the shaded area), is provided in FIG. 4A.Optionally, the downstream end of D1 is located within a counter bore offirst reactor 7, as shown in FIG. 5. At least a portion of the secondreactant is conducted through conduit 3051 to second plenum 206B, whichdirects the flow of the oxidant to channel 16 within first reactor 7. Aportion of the second reactant in channel 16 is consumed oxidizingcombustible non-volatiles located therein. The first reactant andunreacted second reactant combine in region 13 to produce the fourthmixture (for the exothermic reaction) in proximity to the downstream endof first reactor 7, upstream and downstream being defined for theoxidation intervals with respect to the average flow of the fourthmixture and components thereof. The fifth mixture is directed by plenum206A to conduit 2066, and conducted away from the regenerative,reverse-flow pyrolysis reactor. At least a portion of the heat ofcombustion of combustible non-volatiles in stage 206 and the firstreactant's fuel component is utilized to increase the temperature ofregion 2064. In embodiments where the second reactant reacts with asignificant amount of combustible non-volatiles in the passages of firstreactor 7, the upstream end of region 2063 may be located to the left(upstream) of the position shown in FIG. 4.

Optionally, the size and locations of distributor D1 are selected tolessen the amount of mixing of first and second reactant upstream ofregion 13. Optionally, the size and locations of D1 are selected tosubstantially equalize (within, e.g., +/−25%, such as +/−10.0%) the gasvelocities of the first reactant through the passages of channel 14 andthe second reactant through the passages of channel 16. Optionally, thenumber and cross-sectional areas of passages comprising channels 14 and16 are selected to approximately equalize (within, e.g., +/−25%, such as+/−10.0%) the ΔP among the channels.

Oxidation Step—Second Interval

During the second interval of the oxidation step, valves V4, V5, and V6are closed. Valves V8 and V7 are open. Since the first reactant isblocked from distributor D1 by valve V4, the first reactant does notflow into (or emerge from) D1 during this interval. A first portion ofthe second reactant flows from conduit 3051 via gap 20 betweendistributor D1 to channel 14. Although gap 20 as shown in FIG. 5 islocated within a counter bore of first reactor 7, the invention is notlimited to this configuration. For example, when face 9 of first reactor7 is substantially flat (e.g., has little or no counter bore oppositethe adjacent face of D1), gap 20 is the space located between face 9 andthe adjacent face of D1. The first portion of the second reactantoxidizes combustible non-volatiles located in channel 14. A secondportion of the second reactant flows from plenum 206B into channel 16.The second portion of the second reactant oxidizes any combustiblenon-volatiles as might remain in the channel after the first interval.As is the case in the first interval, the fifth mixture can be conductedaway from stage 206.

Optionally, (i) the first portion of the second reactant comprises 30.0wt. % to 70.0 wt. % of the second reactant and (ii) the second portionof the second reactant comprises 30.0 wt. % to 70.0 wt. % of the secondreactant, the weight percents being based on the total weight of thesecond reactant provided to stage 206 in the second interval.Optionally, the weight ratio of first amount:second amount is in therange of 0.5 to 2.0, e.g., about 0.8 to 1.2. Optionally, the size andlocation of distributor D1 and plenum 206B are substantially the same asin the first interval.

Generally, the time duration of first interval t_(2a)+t_(2b) is selectedto accomplish regeneration of first reactor 7. Time intervals t_(2a) andt_(2b) can be independently selected. For example, in an embodiment, thetime duration of second interval t_(2b) is greater than or equal to theamount of time needed for removing ≧50.0 wt. %, e.g., ≧75.0 wt. %, suchas ≧90.0 wt. % of the combustible non-volatiles accumulated in channel14 over a sequence of preceding pyrolysis step(s). The weight percentsare based on the total weight of combustible non-volatiles accumulatedin channel 14 over a sequence of preceding pyrolysis step(s) (and firstinterval(s) when the first reactant can deposit combustiblenon-volatiles). Should combustible non-volatiles deposit in D1, e.g.,during the first interval, these can be removed by conducting oxidantthrough D1 during the second interval. The oxidation step can comprisethe first and second intervals only, but the invention is not limitedthereto. For example, in an embodiment, the first interval and secondinterval are repeated in sequence, one after the other, with nointervening pyrolysis step, until the desired time duration for theoxidation step is achieved. Optionally, t_(2a) and t_(2b) are each inthe range of 0.1 seconds to 15.0 seconds.

The invention is not limited to embodiments where the channels in thefirst reactor 7 comprise two contiguous regions only. For example, inother embodiments, first reactor 7 comprises a honeycomb monolith in theform of an elongated polygonal body. The honeycomb comprises at leasttwo sections, the sections being in side-to-side contact, with eachsection having, e.g., (i) at least one multi-purpose channel and (ii) atleast a portion of those passages of reactor 7 constitutingsecond-reactant channel(s). In one embodiment, first reactor 7 is ahoneycomb in the form of an elongated rectangular body having upstreamand downstream faces of substantially equal rectangular cross-sections.The honeycomb comprises four sections S₁-S₄ joined side-to-side, thesections each being honeycombs in the form of an elongated rectangularbody having upstream and downstream faces of substantially equalrectangular cross-sections. In this embodiment, each section comprisestwo sets of passages, with one set of passages (“S_(mp)”) constituting amulti-purpose channel and the second set of passages (“S_(sr)”)constituting a portion of reactor 7's second-reactant channel. SetsS_(mp1) and S_(sr1) are located in S₁, sets S_(mp2) and S_(sr2) arelocated in S₂, sets S_(mp3) and S_(sr3) are located in S₃, and setsS_(mp4) and S_(sr4) are located in S₄. Sets S_(mp1), S_(mp2), S_(mp3),and S_(mp4) each constitute a multi-purpose channel: C₁, C₂, C₃, and C₄.Sets S_(sr1), S_(sr2), S_(sr3), and S_(sr4) constitute onesecond-reactant channel: C₅. Channels C₁-C₄ are of substantially equalcross-sectional area and have openings located within a circular regionapproximately centered on the faces of sections S₁-S₄ (C₁ centered onthe face of S₁, C₂ centered on the face of S₂, etc.).

The oxidation step comprises four intervals, during which the flow offirst and second-reactants is sequenced as follows:

-   (i) During the first interval, the first-reactant is conducted    through C₁, C₂, and C₃. A first portion of the second-reactant is    conducted through C₄.-   (ii) During the second interval, the first-reactant is conducted    through C₁, C₂, and C₄. A first portion of the second-reactant is    conducted through C₃.-   (iii) During the third interval, the first-reactant is conducted    through C₁, C₃, and C₄. A first portion of the second-reactant is    conducted through C₂.-   (iv) During the fourth interval, the first-reactant is conducted    through C₂, C₃, and C₄. A first portion of the second-reactant is    conducted through C₁.

During each of the first-fourth intervals, the first portion of thesecond reactant is conducted through one of the multipurpose channels(C₁-C₄), the volumetric flow rate of this portion being roughlycomparable (after adjusting for viscosity) to the volumetric flow rateof ⅓ of the first reactant, which is the amount of first reactant thatflows in each of the other multipurpose channels (C₁-C₄), in order tomaintain roughly comparable pressure drop among the passages. A secondportion of the second reactant comprising roughly the remainder of thesecond-reactant is conducted through C₅, in an amount that depends,e.g., on the amount of diluent (if any) in the first and secondreactants; typically ≧50.0 wt. %, e.g., ≧75.0 wt. %, such as ≧90.0 wt. %based on the weight of the second reactant. Optionally, the flow ratesof first reactant, second reactant, and the first and second portions ofthe second reactant are substantially the same (+/−25.0%, e.g.,+/−10.0%) during each interval. When flow rates are substantiallyconstant over the intervals, the relative amount of a given stream thatis conducted during a given interval (e.g., the amount of first reactantthat is conducted during the first interval) will be in proportion tothe duration of the interval. The use of a plurality of sections can beadvantageous when it is desirable to combine and react at least aportion of each of the first and second reactants during all intervalsof the oxidation step.

The use of multiple honeycomb sections (as in S₁-S₄) facilitates theapplication to large-diameter reactor systems. In some embodiments, eachsection utilizes one mixer in region 13 to facilitate mixing of thefirst and second reactants that are flowing predominantly through thepassages in that section. In those embodiments, there may be roughly thesame number of mixers as there are sections. In large-diameter reactors,the number of sections may be very large, numbering in the dozens oreven hundreds. Since a set of passages in each section (the S_(sr))conveys the second reactant, such embodiments do not require a separateoxidation step interval for each section. For example, in oneembodiment, the reactor system comprises (i) a first reactor comprising100 sections and four divisions (25 sections per division) and (ii) onemixer per section. In such an embodiment, the oxidation step cancomprise four intervals, e.g., with multipurpose channel C₁ comprisingthe combination of all the multipurpose passages in the 25 sections ofthe first division, e.g., S_(mp1) to S_(mp25), and multipurpose channelC₂ comprising the combination of all the multipurpose passages in the 25sections of the second division, e.g., S_(mp26) to S_(mp50), etc. Eachof channels C₁-C₄ may be fed by a single distributor, e.g., with 25spargers, e.g., one for each section. The combination of all the sets ofsecond-reactant passages, S_(sr1), to S_(sr100) constitute onesecond-reactant channel (C₅). A combination of hydrodynamic andmechanical valving can be utilized to direct the flow of the firstreactant and first portion of the second reactant to channels C₁ and C₄as described above for the four-section embodiment. A second portion ofthe second reactant can flow to C₅ during all four intervals.

Mixing means suitable for combining the first and second reactantsduring the first-fourth intervals are described in U.S. Pat. No.7,943,808. FIG. 4 of that patent illustrates mixing means suitable foruse with a first reactor 7 comprising a honeycomb having 7 sections,though this embodiment is not limited to that configuration. FIG. 4Athat patent illustrates mixing means suitable for use with single ormultiple sections. Other suitable mixing means for single or multiplesections are shown in FIGS. 4, 5, and 6 of U.S. Pat. No. 7,815,873. Forexample, when a honeycomb of four sections is used, a mixer of the typeillustrated in U.S. Pat. No. 7,943,808's FIG. 4A can be located in eachsection, each mixer being approximately centered with one of C₁, C₂, C₃,or C₄ on an axis parallel to the honeycomb's long axis.

The oxidation steps of the preceding embodiments can be utilized in anyof the pyrolysis reactor systems of stage 206. Referring now to FIG. 1,when it is desired to (a) increase the relative amount of one or more ofhydrocarbon (e.g., methane) and/or hydrogen in the fuel over that of itssource material or (b) increase the relative amount of oxidant (e.g.,oxygen and/or ozone) in the oxidant over that of its source material,this can be done as follows:

-   (a) Hydrocarbon, such as light saturated hydrocarbon, e.g., methane,    can be added via conduit 3001. These species can be obtained    from (i) external sources and/or (ii) sources within the process,    such as from conduits 3081 or 2083, e.g., when optional stages 308    and 208 are utilized.-   (b) Oxidant can be added via conduit 3003. The added oxidant can be    obtained from (i) external sources and/or (ii) sources within the    process such as from conduit 3082, e.g., when optional stage 308 is    utilized and the oxygenate in conduit 3082 comprises oxidant. When    the source material is air, the air can be obtained from a blower or    compressor, for example.

Continuing with reference to FIG. 1, at the conclusion of the oxidationstep optional upgrading stage 308 can be used, e.g., to separate fromthe fifth mixture species that may be useful in other stages of theprocess, e.g., via conduits 3081-3083 as discussed, e.g., diluent can beseparated from the fifth mixture and utilized to produce the fourthmixture. At the conclusion of the pyrolysis step, optional upgradingstage 208 can be used, e.g., to separate from the second mixture speciesthat may be useful in other stages of the process, e.g., via conduits2082. The portion of the second mixture that is not used in other stagesof the process can be conducted away from the process via one or moreconduits (2087) for storage or further processing. Conventionalseparations processes are useful for stage 208 and 308, though theinvention is not limited thereto.

Pyrolysis Step

After the oxidation step, the pyrolysis portion of the first mixture isconducted via conduit 2046 to the upstream end of region 2064, e.g., theupstream end of the second reactor, where upstream is now defined withrespect to the flow of the first and second mixtures. Referring to FIG.4, plenum 206A distributes the first mixture into the channels of secondreactor 1, which have been heated by the preceding oxidation step.Optionally, a reactor purge can be used between the oxidation andpyrolysis steps. During the pyrolysis step, valves V4, V7, and V8 areclosed. Valves V5 and V6 are open. The vapor-phase portion of the secondmixture is directed away from region 2064 by plenum 206B, thevapor-phase portion of the second mixture being conducted away viaconduit 2065. A second portion of the second mixture, comprisingcombustible non-volatiles, remains in the reactor system as a deposit,e.g., in channels 14 and 16.

At the start of the pyrolysis step, (a) the downstream end 5 of thesecond reactor 1 (downstream with respect to the flow of the firstmixture, as shown in FIG. 4) is at a temperature greater than that ofthe upstream end 3 and (b) at least a portion (including the downstreamend 9) of the first reactor 7 is at a temperature less than that of thedownstream end of the second reactor 5 in order to provide a quenchingeffect for the second mixture.

The first mixture is exposed to a temperature ≧1.20×10³° C., e.g.,≧1.50×10³° C., under high-severity thermal pyrolysis conditions.Generally, the first mixture is exposed to these conditions in theportion of region 2064 that is coextensive with region 2063 viaproximity to the second reactor and other reactor internals (e.g., mixermedia) located, e.g., in the temperature profile region, which have beenheated, such as by the exothermic reaction of the fuel and oxidantduring a preceding oxidation step. Optionally, at least a portion of thetemperature bubble region is located within the portion of zone 2064that is coextensive with zone 2063.

Continuing with reference to FIG. 4, the first mixture abstracts heatfrom the first reactor, resulting in the derivation of the secondmixture from the first by pyrolysis. As this step proceeds, a shift inthe temperature profile occurs, e.g., a shift in at least a segment ofthe right-hand edge of the temperature profile (the segment beingschematically encompassed by a dashed boundary for the purpose ofillustration), the direction of the shift being indicated by arrow 2.The amount of this shift can be influenced by, e.g., the heat transferproperties of the system. At least a portion of the second mixture,e.g., the portion in the vapor phase, is conducted from the downstreamend 5 of the second reactor to the upstream end 11 of the first reactor7, and is conducted away from the first reactor via conduit 2065proximate to the downstream end 9, as shown. At the start of pyrolysis,the first reactor 7 has a temperature less than that of the secondreactor 1. As the second mixture traverses the first reactor 7, thesecond mixture is quenched (e.g., cooled) to a temperature approachingthat of the downstream end 9 of the first reactor. As the second mixtureis quenched in the first reactor 7, at least a segment of the left-handedge of the temperature profile moves toward the downstream end 9 of thefirst reactor 7 as indicated by arrow 4, the segment being schematicallyencompassed by a dashed boundary for the purpose of illustration. In atleast one of the embodiments represented by FIG. 4, the upstream end ofpyrolysis region 2064 is proximate to the upstream end 3 of the secondreactor 1. The downstream end of pyrolysis region 2064 is proximate tothe downstream end 9 of the first reactor 7. Since the quenching heatsthe first reactor 7, the oxidation step optionally includes cooling thefirst reactor, e.g., to shift at least a segment of the left-hand edgeof the temperature profile away from end 9 of the first reactor 7, asillustrated schematically by arrow 8 in FIG. 4.

In an embodiment, the pyrolysis step includes one or more of thefollowing conditions: the first mixture achieves a peak pyrolysis gastemperature ≧1.40×10³° C., e.g., in the range of 1.45×10³° C. to2.20×10³° C., such as, 1.50×10³° C. to 1.90×10³° C., or 1.60×10³° C. to1.70×10³° C.; a total pressure ≧1.0 bar (absolute), e.g., in the rangeof 1.0 bar to about 15 bar, such as in the range of 2.0 bar to 10.0 bar;a high-severity residence time ≦0.1 seconds, e.g., ≦5.0×10⁻² seconds,such as ≦5.0×10⁻³ seconds and/or a t₁ in the range of 1.0×10⁻³ secondsto 10.0 seconds. Optionally, the first mixture comprises ≧0.01 mole % ofhydrocarbon, e.g., 0.1 mole % to 90.0 mole % of hydrocarbon and ≧0.01mole % of molecular hydrogen, e.g., 0.1 mole % to 90.0 mole % ofmolecular hydrogen, the mole percents being based on the sum of thenumber of moles of hydrocarbon and hydrogen in one mole of the firstmixture. When it is desired to increase the amount of one or more ofmolecular hydrogen, hydrocarbon (e.g., light saturated hydrocarbon suchas methane), and diluent in the first mixture, these can be added (e.g.,in stage 204) as follows:

(i) Molecular hydrogen can be added via conduit 2043, with the addedhydrogen obtained, e.g., from one or more of (a) from the process viaconduit 2082 when optional stage 208 is present, (b) from molecularhydrogen separated from the first product, or (c) from an externalsource.

-   (ii) Hydrocarbon can be added via conduit 2044. These species can be    obtained from the process via conduit 3081 or 2083, e.g., when    optional stages 308 and 208 are utilized, from hydrocarbon separated    from the first product, or from an external source.-   (iii) Diluent (such as oxygenate) can be added via conduit 2045. The    diluent can be obtained, e.g., (a) from the process via conduit    3082, when optional stage 308 is utilized, (b) from the first    product, (c) from the second mixture, and/or (d) from a source    external to the process.

All patents, test procedures, and other documents cited herein,including priority documents, are fully incorporated by reference to theextent such disclosure is not inconsistent and for all jurisdictions inwhich such incorporation is permitted.

While the illustrative forms disclosed herein have been described withparticularity, it will be understood that various other modificationswill be apparent to and can be readily made by those skilled in the artwithout departing from the spirit and scope of the disclosure.Accordingly, it is not intended that the scope of the claims appendedhereto be limited to the examples and descriptions set forth herein butrather that the claims be construed as encompassing all the features ofpatentable novelty which reside herein, including all features whichwould be treated as equivalents thereof by those skilled in the art towhich this disclosure pertains.

When numerical lower limits and numerical upper limits are listedherein, ranges from any lower limit to any upper limit are contemplated.

The invention claimed is:
 1. A regenerative, reverse-flow pyrolysisreactor comprising, (a) first and second reactors, each comprising aunitary reactor bed; (b) a mixing region located between the first andsecond reactors; (c) first and second channels located within the firstreactor, the first and second channels being thermally-connected,substantially independent flow-paths; (d) a third channel located withinthe second reactor; and (e) first valve means for directing to themixing region (i) a first reactant via the first channel during a firsttime interval, (ii) a second reactant via a second channel during thefirst time interval, and (iii) a first portion of the second reactantvia the first channel and a second portion of the second reactant viathe second channel during a second time interval.
 2. The regenerative,reverse-flow pyrolysis reactor of claim 1, further comprising secondvalve means for directing a hydrocarbon-containing feed to the secondreactor for pyrolysis.
 3. The regenerative, reverse-flow pyrolysisreactor of claim 1, wherein at least one of the first or second valvemeans comprises hydrodynamic valve means including at least one sparger.